Courtesy of the article by John Lister:
A new email virus to watch out for comes in the form of a supposed Microsoft Update, complete with an attachment that download a virus to your machine. Like malware of this kind, it then infects your contacts list and sends itself to as many other machines as possible.
The file is often identified as “KB453396-ENU.exe”, which you’ll notice is a similar name format to actual Microsoft Updates. The thing to remember is that Microsoft never sends updates by email in this way. Only trust updates downloaded from Microsoft.com or by using your Microsoft Update tool in Windows.
To some, avoiding emails such as this may seem obvious. However, it’s important to point out that even a small number of people making the mistake of opening dangerous attachments can end up infecting large numbers of people.